viafb: Autoload on OLPC XO 1.5 only

viafb: Autoload on OLPC XO 1.5 only

Bug-Debian: https://bugs.debian.org/705788
Forwarded: no

It appears that viafb won't work automatically on all the boards for
which it has a PCI device ID match.  Currently, it is blacklisted by
udev along with most other framebuffer drivers, so this doesn't matter
much.

However, this driver is required for console support on the XO 1.5.
We need to allow it to be autoloaded on this model only, and then
un-blacklist it in udev.

Gbp-Pq: Topic bugfix/x86
Gbp-Pq: Name viafb-autoload-on-olpc-xo1.5-only.patch